# Introduction To Periodic Motion

We can classify the motion of various bodies on the basis of the way they move. For example, a car moving on a straight road is said to have linear motion. Similarly, the motion of the earth around the sun is circular motion. Here we will be talking mainly about periodic motion. A motion that repeats itself after equal intervals of time is known as periodic motion. Examples of periodic motion are a tuning fork or motion of a pendulum if you analyze the motion you will find that the pendulum passes through the mean position only after a definite interval of time. We can also classify the above motion to be oscillatory. An oscillatory is a motion in which the body moves to and fro about a fixed position. So an oscillatory motion can be periodic but it is not necessary.

So taking an example of a wave motion we will see some parameters related to periodic motion. Let’s take the following figure:

## Periodic Motion Formula

Time Period (T): It is the time taken by the motion to repeat itself. So the unit of a time period is seconds.
Frequency (f): It is defined as a number of times the motion is repeated in one second. The unit of frequency is Hz (Hertz). Frequency is related to Time period as:

 $f=\frac{1}{T}$

Above is the formula used for periodic motion.

## Simple Harmonic Motion

We also have heard of something known as simple harmonic motion. What is a simple harmonic motion? It is actually a periodic motion having some relation between the restoring force and displacement from the mean position. We will be discussing this motion in detail you can take a look at the introduction to SHM.